The present invention relates to a derrick, comprising a number of hydraulic cylinders arranged in groups having pistons and associated extendible piston rods for axial movement of a drill stem in the derrick, where the piston rods are mutually rigidly connected to each other at their upper ends with a bridge portion.
The present invention is particularly designed for use in drilling operations at sea, but will also be able to find application in drilling operations on land. The aim is the application of the derrick in connection with inter alia hydraulic well overhauling, so-called xe2x80x9cslime hole drillingxe2x80x9d, drilling of multilateral completion drilling of side rungs, and the like.
During the guiding down of the pipe line/drill stem in a well hole, during the drilling operation and on maintenance of a well hole (xe2x80x9cwork-overxe2x80x9d) or in other current operations, it is usual to join together one after the other a series of following pipe sections in the derrick in extension of the pipe line/drill stem and to dismantle in the derrick one after the other a series of pipe sections from the pipe line/drill stem. The joining together takes place by installing the pipe sections individually one after the other in the derrick and that the lower end of the pipe section is joined together with the pipe line/drill stem by turning the pipe section relative to the pipe line/drill stem. The joining together occurs via equivalent thread portions in two mutually abutting pipe sections, and the joining together is followed by a guiding down of the joined pipe line/drill stem towards the bottom of the well hole.
Correspondingly on bringing up of the pipe line/drill stem from the well hole it is usual to dismantle the pipe line/drill stem in the opposite consecutive order by withdrawal of the pipe sections individually, one after the other, after a preceding stepwise hoisting of the pipe line/drill stem.
Generally the hoisting has hitherto taken place with a relatively complicated hoisting device comprising a winch with several parallel hoisting portions. The known hoisting device has a tendency to increase to an unnecessary degree the working time for each operation of joining together and thereby correspondingly reduces the working capacity and increases costs. In certain phases of leading down this can occur by means of the weight of the pipe line/drill stem. In the remaining phases of the guiding down of the pipe line/drill stem there is a need for an extra pushing force on the pipe line/drill stem in addition to the weight of the pipe line/drill stem. This creates extra complications on existing procedures of guiding down pipes. In addition extra equipment is required for controlling the guiding down with a pushing force.
In each drilling operation and each bringing up of the pipe line/drill stem from the oil well and subsequent guiding down of the same towards the well, there is a question about separately handling a large number of pipe sections individually. The time which is involved for each pipe section in the down-guiding operation and the operations of joining together and in the bringing-up operation and the operations of dismantling are of great significance for the collective working capacity and the costs following from this. With the present invention the aim is a solution, which can reduce the working time and thereby increase the working capacity, particularly in connection with the operations of joining together and the dismantling operations, but in addition also in the bringing up and guiding down of the pipe line/drill stem.
The movement of a pipe line/drill stem and a pipe section in an axial direction in the drill rig has, as mentioned above, hitherto proceeded by means of a winch with associated hoisting line portions. In an introductory phase of the guiding down of the pipe line/drill stem it is customary to exert an axial pressure (xe2x80x9csnubbingxe2x80x9d) against the pipe line/drill stem via extra equipment which can exert pushing forces in the pipe line/drill stem in addition to the weight loading in the same, while in a later phase of the guiding down it is customary to relieve the weight of the pipe line/drill stem via the hoisting winch.
With the present invention a particular aim in connection with the afore-mentioned, is to combine the bringing-up and guiding-down operations into one and the same means, that is to say to replace the hoisting devices (winch and hoisting line portions) and the equipment producing said extra pushing force by one and the same means.
The derrick according to the invention is characterized in that the derrick, in addition to the first mentioned group of hydraulic cylinders, comprises additionally, groups of hydraulic cylinders arranged above each other with respective piston rods connected in upper bridge portions, each group of above-standing cylinders being carried by the bridge portion of the group standing below, that each group of cylinders in arranged around a central space for the drill stem, and the derrick carries arrangements for rotation of the drill stem, said arrangements being releasably fixed to the bridge portion for the uppermost group of pistons.
By combining, according to the invention, the hoisting operations and the guiding-down operations (with and without pushing force) in one and the same group of hydraulic cylinders, several significant advantages are achieved, both constructionally and operatively. Consequently by the afore-mentioned solution fundamental advantages can be achieved of a working as well an economic kind.
By employing, according to the invention, groups of hydraulic driven pressure medium cylinders arranged vertically above each other, the single pipe section can be moved in an intended stepwise manner or in a more or less continuous manner in opposite directions according to need in the derrick, independently of what forces which are to be transferred to the pipe line/drill stem. The movements can be carried out according to the invention during the exercise of greater or smaller tractive forces or pushing forces, as required, with one and the same equipment.
By employing a number of cooperating hydraulic cylinders placed in groups above each other in the derrick, the collective power transmission of several hydraulic cylinders can be distributed in each height level of actual interest in the derrick and the collective length of movement distributed correspondingly of several hydraulic cylinders following axially in the height of the derrick.
Consequently the axial movements of pipe sections or pipe line/drill stem in the derrick can be carried out in an especially controlled and reliable manner and yet with a relatively high speed. With the derrick according to the invention movements over relatively large heights can consequently be effected in the derrick with regulatable stages of movement and lengths of movement and with regulatable speeds of movement and regulatable actuation forces, as required.
By arranging the hydraulic cylinders, according to the invention, in two or more vertical rows there can be arranged a guiding of the pipe section centrally between the rows and provided at the same time a favorable constructional mutual reinforcing and shoring up of the hydraulic cylinders relative to the pipe line/drill stem.
By connecting the groups of hydraulic cylinders according to the invention in rigid connection with each other, that is to say with a mutually reinforcing connection, by means of associated rigid bridge portions at different height levels in the derrick, it is possible to subject the drill stem/pipe line or the pipe section to lifting or lowering movements in a favorable manner with sufficient safety and stability.
There is preferred in practice a particular constructional arrangement of the rows of power means. In this connection the arrangement according to the invention is characterized in that the cylinders in each group are mounted in the form of a triangle equally spaced relative to each other.
Further for constructional and reinforcing reasons it is preferred that the cylinders in the uppermost group have the least mutual spacing, and the cylinders in the lowermost group have the greatest mutual spacing.
Further for constructional and reinforcing reasons it is preferred that each bridge portion is supported and reinforced via guide rails in the derrick per se and via control means, such as steering rollers, in the bridge portion.
In practice provision is made for the bridge portion or each bridge portion, in addition to the fastening for the one end of the piston rods of the cylinders of the associated group, to form a fastening for cylinders of an above group or form a guide for piston rods of an additional group which pass through the bridge portion.
The derrick according to the invention is further characterized in that each bridge portion is provided with a laterally opening passage for sideways installation and sideways removal of a pipe section of the drill stem in the space between the group of cylinders, and that the recess is closeable with stop means for shutting off a section of the drill stem with side support in a guide in the recess.
The derrick according to the invention is further characterized in that the arrangements for rotation of the drill stem are arranged in a separate carriage, which is designed for separate handling of a drill stem section relative to the remaining drill stem, the carriage in a first position being releasably fixable to the bridge portion for an uppermost group of cylinders"" piston rods, while the carriage in a second position is separately parkable at a distance from said bridge portion.